The present disclosure relates in general to semiconductor manufacturing technology, and more particularly, the present disclosure relates to beam lithography in semiconductor manufacturing technology. The present disclosure also relates to an improved aperture design for improving accuracy of critical dimension of an angle line and throughput of electron beam lithography.
In semiconductor manufacturing technology, electron beam (e-beam) lithography is commonly used to create a complex pattern on a reticle. Generally, electrons from electron source are accelerated and focused in the shape of a beam toward the reticle. The electron beam is scanned in the desired pattern across an e-beam resist on the reticle surface. The e-beam resist may be a positive-tone poly or a chemically amplified resist.
During e-beam lithography, multiple shots are required in order to create a pattern on the reticle. A shot is produced when the e-beam passes through a plurality of apertures and projects a shape on the reticle surface. Typically, the first aperture is composed of a rectangular shape and the second aperture is composed of at least one bevel. Examples of the shapes projected by the two apertures include a rectangle, a triangle, and a combination of rectangle and triangle. For example, a vertical or horizontal line pattern may be created based only on rectangles, while an angle line pattern may be created based on a combination of rectangles and triangles.
However, the requirement of multiple shots to create these patterns impacts the throughput of e-beam lithography, because multiple shots require a longer period of time to write. In addition, multiple shots make it difficult to align different positions of the shape. In order to correctly align the positions, a bias adjustment procedure is often performed. Bias adjustment utilizes a set of sub-deflectors to deflect the e-beam, such that the positions may be correctly aligned. But as a result of the bias adjustment, the accuracy of critical dimension suffers.
Therefore, a need exists to have an improved aperture design that eliminates the need for multiple shots in e-beam lithography and at the same time preserves the capability of using variable-shaped e-beam.